Surface passivation provided by an alneal through sio2/tio2 bilayer

The process of annealing a SiO2 dielectric layer coated in aluminium, termed the alneal, is known to produce some of the most effective surface passivation for silicon. However, it is traditionally performed on a SiO2 dielectric coating which has sub-optimal anti-reflection properties. In this work it is shown that it is possible to achieve alneal passivation through a double layer SiO2/TiO2 stack. TiO2 was investigated as it is one of the most effective antireflection coatings available and its deposition technology is advanced and cost effective. Here, the alneal was carried out on n-type ~40 Ωcm Cz-Si coated with a SiO2/TiO2 dielectric stack. In the best case, the alneal produced a lifetime increase from ~15 μs to 3084 μs, which equates to a SRV ≤ 10 cm/s or a J0e of 32 fA/cm2. This increase in lifetime was comparable to that achieved by a conventional alneal on a single layer SiO2 specimen. It was also found that the thicker the TiO2, the less effective the alneal was at passivating. Lastly, the passivation achieved after the alneal on the SiO2/TiO2 bilayer was found to be more stable than that achieved on the conventional single SiO2 layer